Dilation of the annulus of the mitral valve prevents the valve leaflets from fully coapting when the valve is closed. Mitral regurgitation of blood from the left ventricle into the left atrium results in increased total stroke volume and decreased cardiac output, and ultimate weakening of the left ventricle secondary to a volume overload and a pressure overload of the left atrium. Dilation of the annulus is sometimes treated by annuloplasty, in which a partial or full ring is implanted around the annulus to cause the leaflets to coapt when the valve is closed.